This invention relates to an arc lamp having a coating on the inside surface of its outer bulb, and more particularly, to a corrective coating placed on the inside surface of the outer envelope of the arc lamp which enhances the warm tones, that is, that in which there is a desired increase in the yellow rendition relation to the blue rendition.
In the prior art it has been known to dispose coatings of inorganic oxide on the lamp envelope to serve various purposes. For example, the U.S. Pat. No. 4,081,709 of C. B. Collins, and myself W. G. James, proves a light-diffusion coating placed on the inner walls of an incandescent lamp by electrostatic deposition.
In the arc tube art there is a need to improve the color rendition of the lamp. It is desired that an arc tube have a color rendition so as to allow a spectral distribution which approaches that of an incandescent lamp having a tungsten type filament. The color rendition of the arc tube has a predominance of a blue-type light emission. The blue-type light emission is not desirable for the arc tube lamp in that the desired color rendition is of a warmer type.
Accordingly, it is an object of the present invention to provide means such as a color correction which lowers the blue-type emission relative to the yellow-type emission so as to provide a more pleasing spectral distribution of the arc tube lamp which is one more nearly having the appearance of a filament source.
These and other objects of the present invention will become more apparent upon consideration of the following description of the invention.